1. Field of the Invention
The present invention relates to a transmission system of differential signals, and more particularly, to a transmission system of a differential signal group.
2. Description of the Prior Art
FIG. 1 is a diagram illustrating a conventional differential signal transmission system 100. The transmission end of the conventional differential signal transmission system 100 comprises a transmission device 110 for transmitting a pair of voltage signals according to the transmitting data (one bit, 0 or 1) through the transmission line pair to the comparator 120 of the receiving end. The comparator 120 compares the voltages of the input ends A and B for generating the received data (0 or 1). For example, when data “0” is transmitted, the transmission device 110 transmits −5 volts on the transmission line A, and +5 volts on the transmission line B. Thus, the comparator 120 compares the voltages on the transmission lines A and B (VA<VB) and outputs data “0”. In this way, the differential transmission is completed. The reason for the conventional transmission system 100 utilizing differential signals is that the differential signals of the same pair have the same common-mode noises and therefore the differential signals of the same pair possess better capability of resisting noises. And because in the differential signal pair, a voltage change in one differential signal has the same amplitude as a voltage change in the other differential signal (and inversed), the electromagnetic interference (EMI) generated by the voltage changes can be reduced. However, in the conventional transmission system 100, a pair of transmission lines only transmits one bit at one time. Therefore, when the data transmission bandwidth requirement becomes substantially large, much more pairs of transmission lines are needed, which costs space and expense.